Nickel base alloys represent an important class of commercial alloys which are commonly used in applications where good mechanical properties are important, such as high temperature strength and corrosion resistance. The art has long sought and continues to actively seek new and improved nickel base alloys where the properties of high temperature strength and corrosion resistance are improved, together with improvement of other mechanical properties such as hot workability, creep resistance and high creep rupture strength.
Typical nickel alloys such as Monel (70% nickel, 30% copper), are found to be highly susceptible to high temperature corrosion known as oxidation-sulfidation when exposed to high temperature gases containing oxygen and sulfur components. The mechanism of the oxidation-sulfidation attack is an intergranular one and the affected alloys often crumble apart. It is obviously highly desirable to provide improved nickel base alloys having good oxidation-sulfidation resistance.
In accordance with U.S. Pat. No. 3,810,754 a series of oxidation resistant nickel base alloys are provided. It is desirable to provide still further improvement in the oxidation resistance of this type of alloys, while providing a combination of good mechanical properties such as good hot workability, good creep resistance and high creep rupture strength.